1. Field of the Invention
The present invention is related to the field of golf clubs and, in particular, to club shafts.
2. Description of Background and Relevant Information
A golf club comprises three main portions, namely, a handle or grip, a shaft, and a head. The shaft can be manufactured in materials such as wood, plastic, metal, or composite materials.
For the purpose of increasing its weight, golf club shafts are more and more often manufactured with the help of tubes made of metal or of composite materials.
The shafts of composite materials, or "composite shafts," are much appreciated by players for the following reasons:
they are lighter than metallic shafts, PA1 their rigidity is easy to optimize as a result of their mode of fabrication.
The gain in mass, obtained by using a composite shaft in place of a metallic shaft, allows the value of this gain to be added to the head for a given club mass. As a result, the impact force on a ball is increased.
The stiffness, most often variable along the shaft, can be optimized by modifying the thickness of the tube in appropriate areas.
In this manner, the flexion of the shaft during a movement of striking the ball will be such that it improves the restitution of the energy contained in the club at the moment of impact.
However, the known composite shafts have the enormous disadvantage of being fragile. The player frequently breaks the club shaft, particularly when the head hits the ground during a striking movement, generally called the "swing."
The swing is a very rapid motion that explains why the forces exerted on the club upon impact are very substantial.
The weight gain on the shaft results in a reduction in the thickness of the tube. The optimization of the stiffness, likewise, results in localized reductions of the thickness of the tube.
It follows that a high-performance composite shaft is fragile and breaks more rapidly than a steel shaft.
The player is therefore obliged to replace his or her equipment more often, which becomes very expensive. Manufacturers have tried to remedy these disadvantages by combining layers of different composite materials and by orienting these layers along selected directions to form the thickness of the tubes. However, the resulting very light shafts are very flexible, but still very fragile.